1. Field of the Invention
The present invention relates to a fuel supply system for a boat and an outboard motor. Specifically, the present invention relates to a fuel supply system for a boat having a fuel supply pump and an outboard motor. The fuel supply pump supplies the fuel contained in a second fuel tank connected to a first fuel tank mounted on a hull to a fuel injection device.
2. Description of the Related Art
Conventionally, a fuel supply system for a boat having a fuel supply pump that supplies the fuel contained in a second fuel tank connected to a first fuel tank mounted on a hull to a fuel injection device is known (See, JP A 2001-140720 and JP A Hei 9-88623, for example).
The fuel supply system for a boat described in JP A 2001-140720 and JP A Hei 9-88623 is a fuel supply system for a boat having an outboard motor. In JP A 2001-140720 and JP A Hei 9-88623, fuel pumped from a fuel tank (first fuel tank) mounted on a hull is contained in a vapor separator tank (second fuel tank). The fuel contained in the vapor separator tank is supplied to a fuel injection device by a fuel supply pump. A regulator is provided between the fuel injection device and the vapor separator tank and is configured such that surplus fuel is returned to the vapor separator tank via the regulator in the case where the pressure of the fuel pumped by the fuel supply pump is larger than a predetermined value. Also, JP A 2001-140720 and JP A Hei 9-88623 use a so-called in-tank fuel supply pump that is disposed in the vapor separator tank. Generally, the in-tank fuel supply pump described above is configured to drive a pump main portion by a motor. In the in-tank fuel supply pump, fuel flows through the inside of the motor when the pump main portion is driven to supply the fuel to the fuel injection device. This configuration makes it possible to cool the heated motor with the fuel.
However, as described above, in the case where fuel flows through the inside of the motor when being supplied to the fuel injection device, the fuel temperature is increased by heat generated by the motor. A portion of the heated fuel is returned to the vapor separator tank by the regulator. Thus, when an engine is continuously operated, the temperature of the fuel in the vapor separator tank gradually increases due to the heat from the motor, which facilitates the generation of vapor (vaporized fuel) in the vapor separator tank. When the engine is stopped after a heavily-loaded operation of the boat, the temperature of the fuel in the vapor separator tank is further increased by heat radiated from the heated engine. This further accelerates vaporization of the fuel, and the vaporized fuel is returned to the fuel tank that is mounted on the hull. In this case, fuel in the vapor separator tank decreases due to the vaporized fuel that is returned to the fuel tank mounted on the hull. For the above reason, because it takes more time to pump fuel up to the vapor separator tank from the fuel tank on the hull during a restart of the engine, it is difficult for the fuel supply pump to efficiently pump fuel up from the vapor separator tank to supply fuel to the fuel injection device. As a result, this hampers smooth engine starting.